Lateral mass fixation system

ABSTRACT

A device for accessing and guiding at least one fixation device to a spine may include a distal portion configured to fit in a facet of the spine and a proximal portion extending from the distal portion. The proximal portion may be detachable from the distal portion and may be hollow or solid. A system for accessing and guiding at least one fixation device to a spine may include a distal portion configured to fit in a facet of the spine, a proximal portion extending from the distal portion, and a slidable guide device for sliding over the facet guide device to guide at least one instrument to the spine.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/004,143, entitled “Lateral Mass Fixation System,” filed on May28, 2014. The full disclosure of the above-listed patent application ishereby incorporated by reference herein.

BACKGROUND

Posterior cervical fusion with lateral mass fixation is the most rigidcervical instrumentation. It requires extensive dissection of musclesand ligaments off the posterior spine, so that the surgeon can havedirect visualization to safely perform the procedure. This dissectioncauses acute and chronic soft tissue pain syndrome. Acutely, patientsare typically hospitalized for three to four days for pain control thatrequires IV narcotics. This is compared to one-day hospitalization foranterior approaches that do not require any muscle or soft tissuedissection. Long-term patients with posterior approaches frequently havepersistent pain due to the extensive nature of the dissection.Sometimes, after posterior-access cervical fusion surgery, soft tissuesmay not return to anatomic position and may be permanently deformed.Persistent pain after posterior surgical approaches is referred to aspost-laminectomy syndrome. (FIG. 1 is a lateral view of the C5 and C6cervical vertebrae, illustrating the anatomy.)

Therefore, since it is considered less traumatic to the patient comparedto posterior approaches, anterior cervical spinal fusion surgery hasgenerally been preferred over posterior fusion surgery. At the sametime, posterior approaches to the cervical spine do have some advantagesover anterior approaches.

Lateral mass or pedicle screw fixation provides more rigid fixation ofthe cervical spine than anterior plates, interbody devices andinterspinous wiring. It is best for traumatic instability, but it hasalso been used for degenerative conditions. Despite being the bestfixation, lateral mass fixation is often avoided, because of themorbidity of the soft tissue dissection, as noted above. (FIGS. 2A and2B are posterior and lateral views, respectively, of a cervical spinewith posterior fixation devices applied thereto.)

Starting a drill hole or inserting a screw into a lateral mass of avertebra cannot currently be accomplished using a percutaneous approach.This is because soft tissue gets caught up in the drill, and the drillcan skid off the bone and go out of control. Awls and firm pressureplaced on bone with screws without direct visualization is dangerous inthe posterior cervical spine, unless the surgeon has removed soft tissueand has direct visualization.

Therefore, it would be advantageous to have improved devices, systemsand methods for performing cervical spinal fusion procedures viaposterior access approaches. Ideally, these devices, systems and methodswould allow for minimally invasive or less invasive access and fixation,as well as helping ensure proper placement of the fixation devices. Atleast some of these objectives will be met by the embodiments describedherein.

BRIEF SUMMARY

The various embodiments described herein provide devices, systems andmethods for accessing the cervical spine via a posterior approach andimplanting a spinal fixation device in the cervical spine. Theembodiments described below generally include a guide device, throughwhich or along which one or more spinal fixation devices may beadvanced. The guide devices described herein generally include a distalend that can be inserted into a cervical facet. Once inserted into afacet, the guide device is relatively stabilized (or “docked”) on thespine and thus can be used as a point of stabilization.

A device for accessing and guiding at least one fixation device to aspine is disclosed. In some aspects, the device includes a distalportion configured to fit in a facet of the spine and a proximal portionextending from the distal portion. In various embodiments, the distaland proximal portions are hollow. In some embodiments, the distal andproximal portions are solid. The distal portion may be removable fromthe proximal portion. In some embodiments, the distal portion includes achamfered or beveled end portion configured to facilitate insertion ofthe distal portion in the facet of the spine. The proximal portion mayinclude a slot formed therethrough for receiving and advancing afixation device to the spine. The end of the proximal portion mayinclude opposing sides having a concave shape and/or opposing sideshaving a convex shape.

A system for accessing and guiding at least one fixation device to aspine is disclosed. In one aspect, the system includes a facet guidedevice, the facet guide device including a distal portion configured tofit in a facet of the spine and a proximal portion extending from thedistal portion. The system further includes a slidable guide device forsliding over the facet guide device to guide at least one instrument tothe spine. The slidable guide device may be rotatable about alongitudinal axis of the facet guide device. The instrument may be adecortication device. The slidable guide device may be a double-barreledor dual-lumen guide tube. The slidable guide device may further includea drill guide having at least one drill path defined therein. Theproximal portion of the facet guide device may have one of a circularcross-sectional shape or a square cross-sectional shape. The proximalportion of the facet guide device may have opposing sides having aconcave shape. The proximal portion of the facet guide device may haveopposing sides having a convex shape. The slidable guide device mayinclude a first tube for sliding over the proximal portion of the facetguide device and a second tube mounted on a side of the first tube forguiding the at least one instrument. The system may further include atleast one bone screw for advancing through the slideable guide device.

A method for implanting a spinal fixation implant is disclosed. Themethod includes advancing a guide device into a facet between twoadjacent vertebrae, advancing a fixation device along the guide device,and attaching the fixation device to at least one of the two adjacentvertebrae. The method may further include attaching the fixation deviceby one of attaching a plate to a facet implant located in the facet orattaching a plate to the two adjacent vertebrae.

These and other aspects and embodiments will be described in furtherdetail below, in reference to the attached drawing figures.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a lateral view of the C5 and C6 cervical vertebrae,illustrating the anatomy.

FIGS. 2A and 2B are posterior and lateral views, respectively, of acervical spine with prior art posterior fixation devices appliedthereto.

FIGS. 3A and 3B are posterior views of a portion of a cervical spine,illustrating insertion of a distal portion of a guide device into afacet between two cervical vertebrae, according to one embodiment.

FIGS. 4A and 4B are posterior views of a portion of a cervical spine,illustrating insertion of a distal portion of a guide device into afacet between two cervical vertebrae, according to an embodiment.

FIGS. 5A and 5B are lateral views of a portion of a cervical spine,illustrating insertion of a distal portion of a guide device into afacet between two cervical vertebrae and removal of a proximal portionof the guide device from the distal portion, according to oneembodiment.

FIGS. 6A-6D are perspective views of a portion of a cervical spine,illustrating a system and method for inserting a lateral mass implant,according to one embodiment.

FIGS. 7A and 7B are perspective views of a portion of a cervical spine,illustrating a system and method for inserting a lateral mass implant,according to an embodiment.

FIGS. 8A-8E are various views of a portion of a cervical spine,illustrating a system and method for inserting a lateral mass implant,according to an embodiment.

FIGS. 9A-9C are various views of a portion of a cervical spine,illustrating a system and method for inserting a lateral mass implant,according to an embodiment.

FIGS. 10A and 10B are perspective views of a portion of a cervicalspine, illustrating a system and method for advancing a decorticatordevice over a guide device, according to one embodiment.

FIGS. 11A-11D are perspective views of a portion of a cervical spine,illustrating a system and method for advancing a drill through a guidedevice, according to one embodiment.

FIG. 12 is a perspective view of a portion of a cervical spine,illustrating a system and method for inserting a lateral mass implant,according to an embodiment.

FIGS. 13A-13N illustrate various views of a portion of a cervical spine,illustrating a system and method for inserting a lateral mass implant,according to an embodiment.

DETAILED DESCRIPTION

The various embodiments described herein provide devices, systems andmethods for accessing the cervical spine via a posterior approach andimplanting a spinal fixation device in the cervical spine. Theembodiments allow for a posterior approach using minimally invasive orless invasive techniques. The embodiments described below generallyinclude a guide tool, through which or along which one or more spinalfixation devices may be advanced.

The surgeon may advance the guide tool into the facet from outside thepatient though a minimally invasive or less invasive incision, and thenmay hold the guide tool via a handle or proximal end residing outsidethe patient. This fixed point deep in the spine can be used to advancedrills, awls, plates, rods and screws, to instrument the posteriorcervical spine other than the facet, from a percutaneous approachwithout direct visualization. This avoids stripping all the soft tissueoff the spine. A fixed point deep in the patient's spine preventsinstruments from slipping off the spine or drills catching soft tissueand skidding out of control. Also, the cervical facet has a fixedanatomic relationship to lateral mass bone consistent in all patients.Instruments can be advanced over the facet tool to reliable landmarks onthe lateral mass without direct visualization.

Some of the devices, systems and methods described herein may include,be performed using, or be similar to one or more components of theDTRAX® Spinal System, from Providence Medical Technology, Inc.(www.providencemt.com). Various components of the DTRAX® Spinal Systemmay be modified or adjusted, according to various embodiments, for usesdescribed herein.

Referring now to FIGS. 3A and 3B, in one embodiment, a facet guide toolor device 10 may include a distal portion 12 configured for insertioninto a facet space between two cervical vertebrae and a proximal portion14 (or “shaft”) that extends proximally from the distal portion 12. Theproximal shaft portion 14 is generally long enough to extend from thedistal portion 12 to a location outside the patient, where it can beheld and manipulated by the surgeon. In one embodiment, the distalportion 12 may include two tines 13. In various embodiments, the distalportion 12 and the proximal portion 14 may either be two attached piecesor may be one piece (e.g. monolithically formed or integrally formed).In some embodiments, the two attached pieces may be detachable, as willbe described further below. In some embodiments, the distal portion 12may be temporary and may be removed once lateral mass fixation isachieved. The distal portion 12 is generally sized and shaped to fitsnugly into the facet and abut the pedicle. The tight fit of distalportion 12 in the facet, due to forces applied by ligaments surroundingthe area, helps provide stability to the facet guide tool 10 whilefixation devices are advanced to the site.

In the embodiment of FIGS. 3A and 3B, the distal portion 12 and proximalportion 14 are hollow, thus forming a central lumen or bore (not visiblein the figures), through which one or more facet fixation devices may beadvanced. Alternatively or additionally, one or more fixation devicesmay be advanced over the guide tool 10 to the cervical spine. Forexample, a fixation device may have a hole formed therethrough ofcomplementary size and shape to the guide tool 10. The hole may bealigned with the guide tool 10 and the fixation device may be advancedalong the guide tool.

With reference to FIGS. 4A and 4B, in another embodiment, a facet guidetool or device 20 may include a distal portion 22 and a proximal portion24. The distal portion 22 may include a beveled edge 23 to aid insertionof the distal portion into a facet. The distal portion 22 and theproximal portion 24 may both be solid, rather than hollow. In thisembodiment, the guide tool 20 acts as a rail, over which one or morefixation devices or other devices may be advanced. In use, the guidetool 20 may be inserted in one facet or in multiple facets during aprocedure. If used in multiple facets, multiple guide tools 20 may beinserted simultaneously, or the same guide tool may be insertedsequentially into multiple facets, to implant lateral mass or pediclescrew spinal instrumentation from a percutaneous approach. According tovarious alternative embodiments, the proximal shaft portion 24 may beflexible or rigid. Its purpose is to extend to the skin surface andserve as a guide for drills, plates, rods, screws and/or other tools ofspinal instrumentation.

Referring now to FIGS. 5A and 5B, in some embodiments, the distalportion 22 of the guide tool or device 20 may be removable from theproximal portion 24, so that the distal portion 22 may be left in thefacet as an implant. In some embodiments, one or more lateral massfixation devices may then be attached to the distal portion 22 forcontacting and attaching to lateral masses of adjacent vertebrae.

With reference to FIGS. 6A-6D, in one embodiment, a system for accessingand attaching fixation devices to a cervical spine facet may include theguide tool or device 20 with distal portion 22 and proximal portion 24,as described above. The system may also include an outer, sliding guidetube 26 and a side-mounted guide member 28 attached to the guide tube26. A screw 30 may be advanced through the side-mounted guide member 28for attachment to bone. As illustrated in FIGS. 6C and 6D, sliding guidetube 26 may be rotated about the proximal portion 24 of the guide device20, to change the position of the side-mounted guide member 28. Thischange of position may be used, for example, to attach two screws to twoadjacent vertebrae. The proximal portion 24 may have differentcross-sectional shapes in different embodiments, with the circularcross-sectional shape providing 360-degree rotation of instrumentsadvanced over it.

Referring to FIGS. 7A and 7B, in an alternative embodiment, a facetguide tool or device 32 may include a distal portion 34 and a proximalshaft portion 36 having a square cross-sectional shape. As illustratedin FIG. 7B, an additional guide device 38 may be advanced over theproximal portion 36 and may include a side-mounted guide tube 39. Inthis embodiment, the square cross-sectional shape of the proximalportion 36 allows instruments to be advanced at a fixed 90 degree angleto the facet surface. This may be useful for lateral mass fixation,because the typical screw fixation is at the midpoint of the lateralmass, which is immediately above the midpoint of the facet.

In yet another embodiment, and with reference now to FIGS. 8A-8E, afacet guide tool 40 may include a distal portion 42 and two or moreproximal shafts 44. A guide system may further include a slidable guideinstrument 46, with a side-mounted guide 48, which may be used toadvance a screw 49 into bone. The proximal shafts 44 may beadvantageous, for example, in advancing multiple guide instruments 46 tothe cervical spine, either simultaneously or sequentially, for attachingscrews to adjacent vertebrae. As illustrated in FIGS. 8D and 8E, theguide instrument 46 may also be rotated over one of the proximal shafts44 to change the position of the side-mounted guide 48 relative to bone.

FIGS. 9A-9C illustrate yet another embodiment of a facet guide tool ordevice 50. Similar to the previously described embodiment, in thisembodiment, the guide tool 50 includes a distal portion 52 and two ormore proximal shafts 54. A guide system may further include a slidableguide instrument 56, with a side-mounted guide 58, which may be used toadvance a screw (not shown) into bone. In this embodiment, the proximalshafts 54 have a square cross-sectional shape. As described above, thesquare cross-sectional shape may be used to orient the guide instrument56 at 90-degree increments.

FIGS. 10A and 10B illustrate another instrument that may be advancedover a facet guide tool or device 20. In this embodiment, a slidableguide tube 60 with a side-mounted decortication device 62 is shownadvancing over the guide tool 20. The decortication tool 62 may be usedto cut or decorticate vertebral bone, as part of a fixation procedure.Various embodiments may include this and/or any other similarinstrumentation, such as but not limited to screws, staples, posts inthe lateral masses, and/or the like. Additional instrumentation, such asa rod or plate, may also be advanced over the facet guide tool 20.Plates generally act as tension bands to connect the rostral and caudalfacet and serves to limit flexion and extension as well as lateralbending.

Referring now to FIGS. 11A-11D, in another embodiment, the facet guidetool or device 20 may be used to advance a double-barreled or dual-lumenguide tube device 70, having a side-mounted tube 72, to the cervicalspine. As illustrated in FIGS. 11C and 11D, in one embodiment, a drill74 may be advanced through the side-mounted tube. This guide tube device70 thus allows for drilling of the lateral mass at the same angle as thefacet.

In yet another embodiment, and with reference to FIG. 12, a facet guidetool 80 may have a distal portion 82 and a proximal shaft portion 84,including a slot 86. The slot 86 may be used for advancing a fixationdevice, such as rod 88 (or plate) and screws 89 for attachment to therostral and caudal lateral mass.

With reference to FIGS. 13A-13N, in one embodiment, a system foraccessing and attaching fixation devices to a cervical spine facet 15may include the guide tool 20 with distal portion 22 and proximalportion 24, as described above (see FIGS. 13A-13B). FIG. 13C illustratesa proximal end 25 of the tool 20 having opposing sides with a concaveshape (A) and a convex shape (B). This shaped proximal end helps tomaximize accessible lateral mass area and to lock the rotationalposition of a sliding guide tube 90 shown in later figures. As indicatedin FIG. 13D and others, the system may also include an outer, slidingguide tube 90 defining a dual-lumen 92 for receiving both a drill guide94 and stylet 96 and the guide tool 20.

In use, and as shown in FIGS. 13D-13F, the sliding guide tube 90 may bepositioned over and slid onto the proximal portion 24 of the guidedevice 20, and docked or otherwise stabilized on or at the superiorlateral mass 100. The stylet 96 may be removed from the drill guide 94(FIG. 13G). FIG. 13H depicts an end view of the guide tool 20 and thedrill guide 94 within the dual lumen 92 of the sliding guide tube 90. Asdiscussed above, the shape of the tool 20 limits rotational movement ofthe guide tube 90. As illustrated in FIG. 13I, the drill guide 94provides one or more guide paths 102 through which a drill, such asdrill 74 in FIG. 11C, may be advanced through the guide 94. This guidetube device 90 thus allows for drilling of the lateral mass at or aboutthe same angle as the facet. After drilling the pilot hole for a lateralmass screw, the drill guide 94 is removed from the guide tube 90 (FIG.13J). As shown in FIG. 13K, a first lumen 104 of the dual lumen tube 90now provides an opening through which a lateral mass screw (not shown)may be guided for insertion in the pre-drilled location. In someembodiments, a secondary guide tube could be used in the lumen 104 tomore precisely guiding the screw to the pre-drilled location.

FIGS. 13L-13N illustrate the guide tool 20, sliding guide tube 90 andthe drill guide 94 inserted in an opposite or rotated orientation (e.g.rotated 180° about the longitudinal axis of the guide tool 20) for useand screw insertion in the inferior lateral mass 106.

The C7 and T1 and T2 facets have a fixed relationship to the pedicle.All of the above devices, systems and methods may be used to cannulatethe pedicle percutaneously, similar to that described for the lateralmass.

All relative and directional references (including: upper, lower,upward, downward, left, right, leftward, rightward, top, bottom, side,above, below, front, middle, back, vertical, horizontal, and so forth)are given by way of example to aid the reader's understanding of theparticular embodiments described herein. They should not be read to berequirements or limitations, particularly as to the position,orientation, or use unless specifically set forth in the claims.Connection references (e.g., attached, coupled, connected, joined, andthe like) are to be construed broadly and may include intermediatemembers between a connection of elements and relative movement betweenelements. As such, connection references do not necessarily infer thattwo elements are directly connected and in fixed relation to each other,unless specifically set forth in the claims.

Although the invention has been disclosed in the context of certainembodiments and examples, the present invention extends beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the invention and obvious modifications and equivalentsthereof. Thus, it is intended that the scope of the present inventionherein disclosed should not be limited by the particular disclosedembodiments described above.

What is claimed is:
 1. A facet guide device for accessing and guiding atleast one fixation device to a cervical spine via a posterior approach,the device comprising an elongated body comprising: a distal portioncomprising a chamfered or beveled end portion configured for insertionin a facet joint of the cervical spine; and a proximal shaft portionextending from the distal portion, and having a first set of opposingsides extending at least a portion of a length of the elongated body,and a shaped proximal end, wherein the shaped proximal end maximizesaccessible lateral mass area, wherein at least one side of the first setof opposing sides has a complementary shape to at least one lumen of aslidable guide device comprising at least two lumens coupled togetherand having parallel and distinct central longitudinal axes, the slidableguide device configured to receive and guide a fixation device to thecervical spine, and wherein the elongated body of the facet guide devicedecreases in height from the shaped proximal end to the distal portionalong the length of the elongated body.
 2. A device as in claim 1,wherein the distal and proximal portions are solid.
 3. A device as inclaim 1, wherein the shaped proximal end of the proximal shaft portionincludes opposing sides having a concave shape.
 4. A device as in claim3, wherein the shaped proximal end of the proximal shaft portionincludes opposing sides having a convex shape.
 5. A device as in claim1, wherein the first set of opposing sides extending at least a portionof a length of the body has a convex shape.
 6. A device as in claim 1,wherein the proximal shaft portion further comprises a second set ofopposing sides extending at least a portion of a length of the body, thesecond set of opposing sides having a concave shape.
 7. A device as inclaim 1, wherein the first set of opposing sides each define a recessextending at least a portion of the length of the elongated body.
 8. Asystem for accessing and guiding at least one fixation device toadjacent vertebrae of a cervical spine via a posterior approach, thesystem comprising: a facet guide device, comprising an elongated bodycomprising: a distal portion comprising a chamfered or beveled endportion configured for insertion in a facet joint of the cervical spine;and a proximal shaft portion extending from the distal portion, andhaving: a first set of opposing sides extending at least a portion of alength of the elongated body, and a shaped proximal end, wherein theshaped proximal end maximizes accessible lateral mass area; a slidableguide device defining at least two lumens coupled together and havingparallel and distinct central longitudinal axes, the slidable guidedevice slidingly received by the facet guide device and configured toreceive and guide at least one instrument to the spine; and a fixationdevice, wherein at least one side of the first set of opposing sides ofthe facet guide device is complementary in shape to at least one lumenof the at least two lumens of the slidable guide device, and wherein theelongated body of the facet guide device decreases in height from theshaped proximal end to the distal portion along the length of theelongated body.
 9. A system as in claim 8, wherein the at least twolumens of the slidable guide device comprise a double-barreled ordual-lumen guide tube.
 10. A system as in claim 8, further comprising adrill guide having at least one drill path defined therein, the drillguide configured to be received by both the slidable guide device andthe facet guide device.
 11. A system as in claim 8, wherein the proximalshaft portion further comprises a second set of the opposing sidesextending at least a portion of a length of the elongated body, thesecond set of opposing sides having a concave shape.
 12. A system as inclaim 8, wherein the first set of opposing sides extending at least aportion of a length of the elongated body has a convex shape.
 13. Asystem as in claim 8, wherein the at least two lumens of the slidableguide device comprise: a first lumen for sliding over the proximalportion of the facet guide device; and a second lumen positionedproximate the first lumen for guiding and receiving the at least oneinstrument.
 14. A system as in claim 8, wherein the fixation devicecomprises at least one bone screw, and the at least one bone screw isadvanced through the slideable guide device.
 15. A system as in claim 8,wherein the fixation device comprises a lateral mass screw or a pediclescrew.
 16. A method for accessing and guiding at least one fixationdevice to adjacent vertebrae of a cervical spine via a posteriorapproach, the method comprising: advancing a guide device into a facetbetween two adjacent vertebrae, the guide device comprising an elongatedbody comprising a distal portion comprising a chamfered or beveled endportion configured for insertion in a facet joint of the cervical spine;and a proximal shaft portion extending from the distal portion, andhaving a first set of opposing sides extending at least a portion of alength of the elongated body, and a shaped proximal end, wherein theshaped proximal end maximizes accessible lateral mass area and at leastone side of the first set of opposing sides is complementary in shape toat least one of at least two lumens of a slidable guide device, the atleast two lumens coupled together and having parallel and distinctcentral longitudinal axes, the slidable guide device configured toreceive and guide a fixation device to the cervical spine and whereinthe elongated body of the facet guide device decreases in height fromthe shaped proximal end to the distal portion along the length of theelongated body; advancing a fixation device along the guide device; andattaching the fixation device to at least one of the two adjacentvertebrae.
 17. A method as in claim 16, wherein attaching the fixationdevice comprises one of attaching a plate to a facet implant located inthe facet or attaching a plate to the two adjacent vertebrae.